The use of wireless communication devices such as wireless telephones, pagers, personal digital assistants, laptop computers, etc. has become prevalent in today's society. In some instances individuals have forgone the traditional POTS service and rely totally on their wireless mobile devices. One of the issues with only having a mobile phone is related to emergency phone calls such as 911 in the Unites States and Canada or 112 in the European Union and the difficulty in accurately locating the mobile device used to place the call. This can be especially challenging if the call originated in a multistory building.
Recently, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position, or “geolocate” a mobile device in certain circumstances. For example, in the United States, the Federal Communication Commission (FCC) has issued a geolocation mandate for providers of wireless telephone communication services that puts in place a schedule and an accuracy standard under which the providers of wireless communications must implement geolocation technology for wireless telephones when used to make a 911 emergency telephone call (FCC 94-102 E911).
In order to support the FCC E911 mandate to locate wireless 911 callers, as well as support other location enabled services, providers of wireless communication services are installing mobile device location capabilities into their networks. In operation, these network overlay location systems generally take measurements on RF transmissions from mobile devices at multiple base station locations surrounding the mobile device, and estimate the location of the mobile device with respect to the base stations. Because the geographic location of the multiple base stations is known, the determination of the location of the mobile device with respect to the base station provides the actual geographic location of the mobile device. The RF measurements of the transmitted signal at the base stations can include the time of arrival, the angle of arrival, the signal power, or the unique/repeatable radio propagation path derivable features (radio fingerprinting). In addition, the geolocation systems may also use collateral information, i.e., information other than that derived for the RF measurement to assist in the geolocation of the mobile device, such as location of roads, dead-reckoning, topography, map matching etc.
In a network-based geolocation system, the mobile device to be located is typically identified and radio channel assignments determined by (a) monitoring the control information transmitted on a radio channel for telephone calls being placed by the mobile device or on a wireline interface to detect calls of interest, i.e., 911, (b) a location request provided by a non-mobile device source, i.e., an enhanced services provider. Once a mobile device to be located has been identified and radio channel assignments determined, the location determining system is first tasked to determine the geolocation of the mobile device and then directed to report the determined position to the requesting entity or enhanced services provider. In addition to the RF measurements, other solutions exist for outdoor environments such as mobile device based A-GPS, AFLT, or network base TDOA, AOA, or various more.
However, repeaters and distributed antenna systems (DAS) further extend coverage into areas where the direct RF penetration from base stations is limited or insufficient. Those areas generally include tunnels, shadowed areas behind mountains, underground train systems, indoor areas, train coaches, ships, and many more. With the increasing use of mobile devices and more emergency calls initiated from a mobile network, accurately locating callers in these extended coverage areas is even more important. For the quick and precise guidance of emergency personnel or the police to the correct location, the exact coordinates of the individual that called 911/112 is important. However, contemporary RF and GPS solutions used in outdoor environments are insufficient to provide the needed location data for some of the extended coverage areas, especially inside buildings and other confined spaces.
Therefore, there is a need in the art for improvements in geolocation systems and methods of operation in a host wireless communication system that provides accurate geolocation of mobile devices served by both base stations and repeater stations.